Moving handrails on an escalator or moving walkway are typically driven by passing the handrails through a driving pressure nip along the return path of travel of the handrail beneath the balustrades. The nip may be formed by a pair of cooperating rollers, or by a driven belt which cooperates with a plurality of backup rollers. The nip will be powered by chains or the like which are driven by the main drive mechanism of the escalator. Soviet Patent No. SU1286-493A, U.S. Pat. No. 4,134,883, and Austrian Patent No. 247,236 disclose variations of the prior art drive systems described above.
When the handrail is contacted directly by rollers in the nip, either drive rollers, backup rollers, or both, a line contact occurs between the handrail and rollers. A large compressive force is thus concentrated in a line and applied to the handrail. These localized compressive forces can weaken the handrail and shorten its useful life. Another problem which occurs when direct roller to handrail contact is used concerns slippage of the rollers relative to the handrail. This slippage is the result of the rollers' speed being in terms of angular velocity while the handrail's speed is present as rectilinear velocity.
Japanese Kokai 52,31479 dated Sep. 3, 1977 relates to a handrail driving device which limits localized bending of the handrail and prevents accumulation of dirt on the exposed surface of the handrail. The Japanese drive uses a reaction belt which contacts the exposed side of the handrail, which belt is looped about two idler rollers and passes over a spring-biased pressure plate which urges the belt against the handrail. The reaction belt thus must be formed with a high coefficient of friction side which contacts the handrail, and a low coefficient of friction opposite side which contacts the pressure plate. Care must be taken not to scuff the handrail with the reaction belt.